German Patent Application No. 37 04 938 discloses a controller with at least one microprocessor and one memory element. The memory element can operate at voltages below the supply voltage of the controller and/or the microprocessor. A status signal polled by the microprocessor is stored in the memory element.
German Patent Application No. 44 09 286 discloses a process and a circuit for detecting the cause of a reset of a microprocessor-controlled system. Also here, a memory element is provided, which does not lose its contents when the supply voltage is briefly interrupted, however, it does lose its contents when shut off for a longer period. Whether the memory element was shut off for a short or a longer period can be verified by reading the memory element voltage.
Since the safety requirements for automotive components are usually very high, the mode of operation of the memory element must be insured at all times.